The present invention relates to an optical recording medium such as an optical disk and a magneto-optical disk capable of recording information in each track formed by a land and a groove provided between the lands, a tilt detector of optical recording medium, an optical disk drive, and a tilt detecting method and tilt correcting method of optical recording medium.
Optical disks include, aside from a read-only optical disk such as a CD-ROM, a direct read after write optical disk capable of recording additionally, a rewritable magneto-optical disk, and a phase change type disk, among others, and larger capacity and higher density are demanded recently along with the progress of the electronic society.
To increase the memory capacity of an optical disk, it has been attempted to shorten the wavelength of the laser beam used for the light beam, and to increase the numerical aperture (NA) of the lens used in the emission of the light beam and the reception of its reflected light. As a result, however, the tolerance for tilt (inclination of an optical disk) has now been narrowed.
In conventional measures for detecting tilt, the light beam was emitted to the optical disk, the tilt amount of the optical disk was detected from the difference in the quantities of light received by two photo sensors mounted on the periphery of the emission lens, and the lens, actuator, entire carriage or the spindle itself was inclined depending on the detection signal, thereby decreasing the tilt amount.
This method was applied, however, only in the optical disk drives not requiring high speed access, such as video discs, and since the mechanism itself is inclined, the response time is slow, and it could not be applied in optical disk drive requiring a high speed access, such as those used in computers.